Japanese encephalitis virus in India: An update on virus genotypes

Area of Science:

• Epidemiology
• Virology
• Public Health

Background:

• Japanese encephalitis (JE) is a major cause of viral encephalitis in Southeast Asia and a significant public health issue in India.
• Despite vaccination programs since 2006 and 2011, JE incidence is escalating in several Indian states, with new cases reported in Odisha.
• A shift in JE virus (JEV) infection age groups to adults in West Bengal and the emergence of new genotypes signal the need for strengthened surveillance.

Purpose of the Study:

• To review the current knowledge on the molecular epidemiology of JEV in India and globally.
• To discuss future research priorities for effective JEV control strategies in India.
• To highlight the public health implications of evolving JEV genotypes and vaccine effectiveness.

Main Methods:

• Review of existing literature on JEV molecular epidemiology.
• Analysis of reported JEV incidence trends and genotype surveillance data from India and global contexts.
• Evaluation of current vaccination strategies against emerging JEV genotypes.

Main Results:

• Escalating JE incidence in specific Indian states (Assam, Uttar Pradesh, West Bengal) and new foci in Odisha.
• Detection of JEV genotype I (GI) and co-circulation of GI and genotype III (GIII) in West Bengal, with GI in Uttar Pradesh.
• Emergence of JEV genotype V (GV) in East Asia and concerns regarding its efficient dispersal and reduced vaccine efficacy.

Conclusions:

• Strengthened surveillance systems are crucial in endemic hotspots due to evolving JEV genotypes and potential vaccine escape.
• Ongoing vaccination strategies require careful evaluation considering the reduced efficacy against JEV genotype V and potential GV incursion.
• Future JEV research in India must focus on molecular epidemiology and control strategies to address the changing landscape of the disease.